Gaseous discharge lamp circuit



l GASEOUS DISCHARGE LAMP CIRCUIT Filed Sept. 18, 1941 INVENTOR GeorgeHow/v ATTORNEYS Patented May 16, 1944 GASEOUS DISCHARGE LAMP CIRCUITGeorge B. Horn, F 'airiield, Conn, assignor, by

.mesne assignments, to The Wheeler Insulated Wire Company; Incorporated,

Bridgeport,

Conn., a corporation of Delaware v Application September 18, 1941,Serial No. 411,279 (Ci. 315-96) V 9 Claims.

This invention relates to electric gaseous discharge lamps orfluorescent tube circuits having a plurality of lamps or tubes therein,and is an improvement over the device disclosed and claimed in my PatentNo. 2,241,261.

In that patent. there is disclosed an arrangementusing anautotransformer for operating a plurality of fluorescent tubes which issatisfactory for many installations. However, it has been found thatunder certain conditions the tempera: ture rise in the transformerbecomes too great and the current requirements for operating the tubestoo high. It has also been found that the wave form in the leading orcapacitive tube deviated substantially from a sine wave.

These difficulties have been overcome by the present invention byinserting a single choke in the primary circuit in. series with andbetween the common point of connection and the alternating supplytherefor.

When the circuit is so arranged, the starting current in both theleading and lagging tubes is reduced to substantially the minimums asset up by the Electrical Testing Laboratories, Inc.,' the runningcurrent of the leading tube is reduced, the temperature rise of thetransformer is greatly reduced, and the wave form of the current in theleading tube is changed to' substantially a sine wave without in any wayaffecting the wave form of the lagging tube which is practically a sinewave. 7

The value of the impedance of'the choke so inserted in the circuit issmall and, within a rea-' I sonable range, not critical as the positionof the coils on the transformer may be shifted tocompensate for suchvariations in the value of the choke, together with suitable changes inthe condenser in the circuit. a

Other features and advantages of the invention will be apparent from thespecification and claims when considered in connection with the drawing,in which:

Figure 1 shows a diagram of the fluorescent tube circuit of the presentinvention.

Figure 2 shows a comparison of the waveforms of the current in theleading tube as produced in an oscillograph. I

In the illustrated form of the invention, the circuit includes twoelectric gaseous discharge lamps r fluorescent tubes in and II havingfilaments Ina, llib, and ilaand lib, at opposite ends thereof.

The filaments are connected in series by means of I starter switchesdiagrammatically shown at I00 and i lc. These switches preferably are ofthe type which automatically close the filament circuit to heat thefilaments to activate the tubes and upon opening cause the tubes to areover.

Each switch remains in open circuit condition as long as there is anelectron flow through the tube between the filaments.

Power for operating the tubes is supplied by a transformer l2 having anelongate core i3, a primary winding I4 and a .pair of secondary windingsI 5 and IS. The windings i4, i5 and ii are shown as being connected toform an autotransformer with the secondary winding l5 connected toenergize the filaments of tube III and the secondary winding l6connected to the filament circuit "of tube Ii to energize them. A

condenser I! is included in one of the tube circuits.

The currents for the two tubes are thus electrically displaced so thatone is leading current and the other lagging. Herein the tubes arereferred to as leading or capacitive tubes and lagging or inductivetubes.

The circuit thus iar described is the same as described in my patentnoted above and is highly satisfactory under normal conditions. However,it has been found, under certain conditions, that the temperature risein the transformer is vtoo great and that the operating currents are toohigh.

,I have "discovered that these difficulties are overcome by inserting achoke coil IS in series with, and between, the common terminal of theprimary and its connection to a sourceof alternating current indicatedat l9.

{The impedance of the choke is relatively low and its value, withinreasonable limits, is not critical as the position of the transformerwindings can be adjusted-on the core and the value of. the condenser l1varied to compensate for slight variations thereof.

The improved results obtained with this new circuit can best ,b shown bya comparative test of it with a circuit omitting the choke. For example,in a test conducted on a circuit having 40 watts output at the tubes, itwas found that a 12 to 15% decrease in temperature rise was obtainedwhen the choke is included in the circuit. When devices of this type areused in places'where ventilation and cooling conditions are bad, this isa substantial advantage.

With regardto the current requirements of the tubes, the running currentin the lagging tube of the circuit without the choke, which we shallcall the former circuit, was ,40 amp., and

with the present circuit was also .40 amp.. in-

F' icE i high maximum value.

dicating that by putting the choke in the circuit there was no change inthe value 01' the running circuit for the lagging tube. However, thecurrent in the leading tube in the former circuit was .44 amp., whereaswith the new circuit it was only .40 amp. Thus it will be seen asubstantial drop in the normal running current in the leading tubecircuit is produced in the present arrangement.

The starting current for the tubes is greatly affected by the inclusionof the choke in the circuit. The Electrical Testing Laboratories, Inc.,has established the minimum and maximum starting currents which areacceptable to tube manufacturers. These limits are minimum .55 amp. andmaximum .75 amp. With the former circuit, the starting current was .70amp. in the lagging tube and .65 amp. in the leading tube. It will benoted that although within the limits specified by the ElectricalTesting Laboratories, Inc., these values are closer-to the upper limits.

With the new circuit, however, the starting current in the lagging tubeis reduced to .58 amp. and in the leading tube to .56 amp., which val-.ues are approximately the minimum specified values.

This reduction of the starting current is particularly valuable in thecase where the starter circuit contacts stick and fail to open thecircuit and also when the tubes become deactivated, that is, where thereis no electron flow between the filaments at the opposite ends of thetube. When this occurs, the starting circuit automatically attempts tobring the filaments to that temperature at which the tube will becomeactivated, and, since the tube will not are over, a

periodic closing and opening of the starting switch will take place withthe attendant flow of starting current.

' With the new circuit, the current demand is substantially reduced andnaturally the temperature of the unit is reduced.

The wave forms of the currents in the two circuits were examined bymeans of an oscillograph. The current in "the" laggin tube was found tobe substantially a sine wave and was not visibly aflected by theinclusion of the choke in the primary circuit. The current in theleading tube,however, in the former circuit was not a sine wave, but hada shape as shown in Fig. 2 by the dot and dash line 20. It will be notedthat it is generally peaked and has a relatively With the choke in theprimary circuit, however, the wave form of the current in the leadingtube took the form shown by the solid line II in Fig. 2, which, it willbe noted, was substantially a sine wave. This new wave i'orm wassubstantially thewave form of the current in the'lagging tube. The waveforms in Fig. 2 were traced from an actual comparison test on theoscillograph. I

This change in wave form is important from an operating standpoint asthe leading tube no longer has a high or peak value but is substantiallythe same as that of the lagging tube.

The foregoing comparison has been made by way of example only and is notintended to limit the scope of the invention.

While the circuit of the transformer is illustrated as that of anautotransformer of the type disclosed and claimed in my patent, thepresent invention is not to be limited to a circuit employing only thistransformer, but may be used with other transformer connections so longas a choke or the like is included in the primary assanso circuit whichaffects the secondary supp yi l the leading tube.

Variations and modifications may be made within the scope of thisinvention and portions of the improvements may be used without others.

I claim:

1. In a circuit for energizing a pair of electric gaseous dischargelamps, means for producing electrically displaced energizing currents, aleading current for one lamp and a lagging current for the other lamp; atransformer having a primary cbil and a pair of secondary coils, all oisaid coils having a common terminal, one secondary coil being connectedto each lamp; and a choke coil in a supply line connected to the commonter- 'minal of the transformer, said choke reducing the operatingcurrent requirements for said tubes.

2. A fluorescent tube circuit having a leading tube and a lagging tubetherein; a source of alternating current; an autotransformer connectedto said source and having a primary coil and a pair of secondary coils,one of the secondary coils being connected to the leading tube and theother secondary coil being connected to the lagging tube to operate saidtubes, said primary and secondary coils having a common terminal; and achoke coil connected in series between the common terminal of theprimary or the transformer and the source of alternating current, saidchoke coil reducing the starting and running current required to operatesaid leading and lagging tube.

3. A fluorescent tube circuit having a leadin tube and a lagging tubetherein; a source of alternating current; an autotransformer connectedto said source and having a primary coil and a pair of secondary coils,one of the secondary coils being connected to the leading tube and theother being connected to the lagging tube to operate said tubes; andmeans for reducing the temperature rise in the transformer for a givenwatt output including a choke coil connected in series with and betweenthe common terminal of the transformer and the source of alternatingcurrent.

4. A fluorescent tube circuit having a leading tube and a lagging tubetherein; a source of alternating current; an autotransformer connectedto said source and having a primary coil and a pair of secondary coils,one secondary coil being connected to the leading tube and the otherbeing connected to the lagging tube to operate said tubes. all of saidcoils having a common terminal; and means for producing substantially asine wave in the/.eurrent in the leading tube comprising a choke coilconnected to the common terminal and in series with the source ofalternating current.

5. .A fluorescent tube circuit having a leading tube and a laggin tubetherein; means for supplying alternating current; an autbtransiormerconnected to said means and having a primary coil and a pair ofsecondary coils, one secondary coil being connected to the leading tubeand the other connected to the lagging tube to operate said tubes, allof said coils having a common termi. nal; and means connected to theprimary coil of the autotransformer for varying the wav form or theleading tube without aflecting the wave form of the lagging tube, saidmeans including a choke coil connected in series between the com--connected to the lagging tube to operate said tubes, all of said coilshaving a common terminal; and means for reducing the operating currentin the tubes for a given watt output at the tubes comprising a chokeconnected between said common terminal of the transformer and the sourceof alternating current.

7. A fluorescent tube circuit having a leading tube and a lagging tubetherein; a source of alternating current; an autotransformer connectedto said source and an autotransi'ormer connected having a primary coiland a pair of secondary coils, one secondary coil being connected to theleading tube and the other connected to the lagging tube to operate saidtubes,

ternating current;

a all of the coils having a common terminal; and means for reducing therunning current in the to said source and having a primary coil andapair of secondary coils, one secondary coil being connected to theleading tube and the other being connected to the lagging tube tooperate said tubes, all of said coils having a common terminal; andmeans for reducin the starting current in both the leading and laggingtubes for a given watt output at the tubes comprising a choke connectedin series between the common terminal of the transformer and the sourceof alternating current.

8. A fluorescent tube circuit having a leading tube and a lagging tubetherein; a source of alleading tube for a given watt output at the tubescomprising a choke connected in series with the common terminal of thetransformer.

9. A fluorescent tube circuit having a leading tube and a lagging tubetherein; a supply of alternating current; an autotransformer having acore, a pair of secondary coils on the core and a primary coil connectedto said source of altemating current, one of the secondary coils beingconnected to the leading tube and the other connected to the laggingtube, all of said coils having a common terminal; and means including achoke conected in thesupply line to the common terminal for reducing thecurrent requirements of each tube for a given watt output at the tubes.

; GEORGE B. HORN.

